Power hammer



April 8, 1924; 1,489,312 J. W. CUNNINGHAM POWERZHAMMER Filed Aug. 21. 1922 2 Sheets-Sheet 1 April 8, 1924; 1,489,312

J. W. CUNNINGHAM POWER HAMMER 1922 2 Sheets-Sheet 2 9 1 maw Patented 8 v UNITED STATES kMunroe-me.

JOHN WILLIAM CUNNINGHAM, OF DETROIT, MICHIGAN, ASSIG'NOR TO CHICAGO PNEfi- MZA'I'IC TOOL'CQ, OF NEW YORK, N. Y., A'COBPOBATION OF NEW JERSEY.

Pownn. HAMMER.

Application filed August 21, 1922. Serial 1T0. 683,118. i

To all whom it may concern:

Be it known that I, JOHN -WInLiAm: CUNNINGHAM, a citizen of the Un ted States, residing at Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Power Hammers, of which the following is a specification.

My invention relates to a power-hammer preferably, though not necessarily, operated chipping, drilling or r veting by means of a chisel, drill, rivet set,'orthe like, to one end of which the striking member of the hammer imparts its blow. A hammer of this general type is disclosed in United States Letters Patent, No. 1,191,948, grant- 7' ed July 25, 1916 to O. B. Coates, and comprises in general a hollow air cylinder directly reciprocated by the electric or other type-of motor and a hammering or impact piston, the reciprocatory motion of the cylinder being imparted to the piston-through the instrumentality of the air above and bea low the piston which delivers a blow at each reciprocation upon the inner end of the shank of the-tool inserted into the front end of the. barrel within which the hollow cylinder is reciprocated, as is well understood in the art. It is customary in this type of hammer, as exemplified in the Coates patin one of the cylinder heads.

cut, to provide the air cylinder with a head on either end and equip the piston with a stem which projects through a central bore I One of the principal objects of my invention is to improve and simplify the construction and operation of this type of hammer and at the same time increase its efiiciency and relia bility. To this end, I have employed a power operated air cylinder which is closed at but one end and contains the reciprocating piston, possessing considera-ble weight and adapted to deliver a sharp, snappy and powerful blow on a tool set through the open end of the cylinder, ports in the cylinder and in communication with the barrel being so positioned and proportioned that the piston is reciprocated with the cylinder in a highly eflicient and efiective manner.

Others features of advantage and utility in my power-hammer will be apparent from the description hereinafter 'ven.

In the drawings, Figure 1 1s a central sectional elevation of my power-hammer and 2' to-7 are like sectional elevations Figs through the barrel and the hollow aircylinder, showing the latter and the piston in the various and successive positions through which they pass during a single cycle of operation of the device.

My hammer is a power-hammer operated preferably directly by a prime mover'located in the hammer structure itself and while any suitable motor may be employed as such prime mover, I prefer an electric motor, and will, therefore, describe my invention in connection with such a motor, so 7 motor has an armature shaft 9 mounted in suitable hearings in the casing Sand formed at its outer'end as a pinion 10 which meshes with a gear 11 secured to the crank shaft 12. This crank shaft is mounted in suitable hearings in a gear case '14 secured to the motor casing. The handle 13 is shaped to receive the grip of the .hand of the operator and is secured in any suitable manner to the motor casing and the gear casing. This handle contains the electric motor switch indicated generally at 15 and provided with a button 15 for convenient operatiom,

The'hammer barrel 16, which may be of suitable dimensions, is adapted to be secured at thelower end of the crank case, this barthe details of construction with suitable hearings to fit the crank pin of the crank shaft 12 and on the other end cost of manufacture. The air cylinder is reduced in diameter intermediate its ends to provide exterior annular flanges 22 at its upper and lower ends and form an annular space or chamber 24 between the innerwalls of the barrel and the exterior walls of the.

cylinder, the flanges 22 being turned to form a sliding fit 1n the bore of the barrel.-

7 The air cylinder 22 is provided with a port ginning wit 25, a port 26 and two ports 27 passing through its Walls and communicating with the interior of the cylinder and the annular space 24.. These 'ports are preferably arranged. in different planes or points axially of the cylinder and whileI preferably employ but one port 25, one port 26 and two rts 27, it will be understood that the numr of the various ports is immaterial and may be increased, so long as they are pr0perl proportioned. Located within the cylin er 22 is a hammering piston .28 which is preferably heavier than the usual piston heretofore employed in this general type of ton 28, the upper end of which has passed and closed the ort 25. The upward move ment of the piston 28 continues until the air trapped by the piston in the upper end of thecylinder 22 is compressed sufliciently to overcome the momentum of the piston. This uppermost extent of movement of the piston is shown in Fig. 3, in which the c linder 22 has been moved downward a .s 'ght extent, thecrank shaft 12 having moved ap roximately 45 degrees past its t this point, the ports u per de center. 2 are uncovered by the lower end ot the iston, so that the annular space 24 and the Interior of the cylinder 22 below the piston are thrown into communication with each other and any loss of air from the annular ace 24, which may have occurred during s t e preceding cycle of operation, is restored so t at the air pressure therein is the same as the pressure inside of the lower end of the barrel. The piston 28 now starts to move downward with the cylinder 22 and its downward movement is accelerated due to the ex nsion of the air trapped in the upper on of the cylinder so that it moves at a more rapid rate than does the cylinder. In Fig. 4 the cylinder22 is beginning to slow down due tov the angular position of the ig. 2, at which time theport 25.

its highrate of speed acquired during'the down stroke of the cylinder. In this figure,

the upper end of the piston is just about clearing the port 25 which is smaller than the port 26 and is so placed that the volume of air in the cylinder 22 above the piston, when'the upper end of the'piston is just closing the port 25,-is approximately equal to the volume of air in the annular space 2 L If it were not for the port 25, the air in the upper end of the cylinder 22 would begin to be rarefied as the piston continues to move downward from'the position shown in Fig. 4 and the partial vacuum produced would retard the speed of the iston and destroy or seriously impair the orce of its blow on the chisel or drill 18. This port 25, however, throws the annular space 24' into communication with the upper end of the cylinder so that the rarefication of the air due to the further downwardv movement of the iston is retarded and When the piston is a vanced slightly to the position shown in Fig. 5, the larger port 26 is uncovered by the piston, which puts the upper end of the cylinder and the annular space% into free permitting the piston to impart the full f power of its blow on the tool 18. Fig. 5

shows the piston at the instant that it strikes the tool, and this occurs just'before the cylinder 22 reaches its lower limit of movement. In Fig. 6. the cylinder 22 is shown at, the limit of its downward movement and the piston has delivered its blow and rebounded to cover the port 26. During that portion of the upstroke of the cylinder from its position shown in Fig. 6 to the positionshown in Fig. 7, the cylinder and piston move substantially in' unison with,

the upper end of the piston just below the During this movement, the air in theupper end of the cylinder and in the annular space 24 is under practically uniform or equal pressure and the position of the piston is just sufiicient to produce a partial vacuum in the upper end of the cylinder and in the annular space 24 enough to overcome the'weight ofthe piston and cause it to be raised with the cylinder. Now, as the cylinder moves from the {position shown in Fig. 7 to its uppermost position, shown in Fig. 2, its movement is retarded and finally comes to rest momentarily, but the piston continues its upper movement at a rapid rate due to its momentum until it is stopped by the air trapped and compressed by it in the upper end of the cylinder which happens during the initial downward extent of movement of the cylinder, as shown in Fig. 3. It is understood, of course, that the lower end of the barrel is properly lower end of the barrel on the down stroke of the cylinder 22 and piston and admission of air to the barrel on the up stroke of the cylinder 22'and piston.

I have shown the hammer held in a vertical position in the drawings and have described the relation of the parts and the directions of movements of the cylinder 22cand piston 28 with the hammer in such position,- but .it will be obvious that the hammer may be used in any desired position, even in an inverted position, inasmuch as the action or the hammer depends largely on the inertia of the piston. i

I claim:

1, In a power hammer, the combination of a barrel, a power operated hollow clyinder arranged to be reciprocated in said barrel, said cylinder having an unrestricted open end, a piston freely movable in said cylinder, and means whereby the reciprocation of said cylinder imparts movement to said piston to deliver blows upon a working tool through the open end of said cylinder.

2. In a power'hammer, the combination of a barrel, a power operated hollow cylinder arranged to be reciprocated in said barrel, said cylinder having an unrestricted open end, a piston freely movable in said cylin er, and means whereby the reciprocation of said cylinder imparts movement to'said piston to deliver blows upon a working tool through the open end of said cylinder, said means including an air chamber alternately put in communication with the closed por- 3 tion' of said cylinder above said piston and the open portion of said cylinder below iston. e

3. na power hammer, the combination of a barrel, a power operated hollow cylinder therein reduced indiameter intermediate its ends to form an annular space between it and the inner walls of the barrel and having its lower end open, a piston freely movable in said cylinder and adapted to have movement'imparted thereto by said cylinder, and ports through the wall of saidv cylinder controlled b said pistonwhereby said space is alternate y placed in communication with the closed portion of said cylinder above iston and the open portion of said der below said piston. v d. In a power hammer, the combination of a barrel, a power operated hollow cylinder thereinreduced in diameter intermediate its ends to form an annular space between it and the inner walls of the barreland having its lower and open, a piston freely movable in said cylinder and adapted to have movement im arted thereto b said cylinder,

said

and means or progressive y establishingcommunication in ter' degree between s and the upper or closed end of C I said cylinder above said piston on the working stroke of/thelatter. V

5. In a power hammer, the combination of a barrel, a power operated hollow cylinder therein reduced in diameter intermediate its ends-to form an annular space between it and the inner walls of the barrel and having its lower'end open, a piston freely movable in said cylinder and adapted to have movement imparted thereto by said cylinder, and ports in the wall of said cylinder successively uncovered by said piston on its working stroke for progressively establishing communication between said space and the up piston. r v

6. In a power hammer, the combination of a barrel, a power operated hollow cylinder therein reduced in 7 diameter intermediate its ends to form' an annular space between it and the inner walls of the barrel and having its lower and open, a piston freely movable in said cylinder and adapted to have movement im arted thereto by said cylinder, and ports di erential in size'in the wall of said cylinder successively uncovered by said piston on its working stroke for progres sively establishing communication between said space and the upper or closed end of said cylinder above said 'iston.

7. In a power hammer, t e combination of a barrel, a power operated hollow-cylinder arranged to be reciprocated in said barrel,

said cylinder "having an unrestricted open end, a Lp1ston'lree1y movable in said cylinder,

and a apted to be reciprocated in responseto the movements of said cylinder, and an air chamber arranged to be 'progressively placed in communication with the closed'end of said cylinder by said piston on its working stroke to permit the latter to. deliver a forceful blow u v n the working tool through the open en of said cylinder. 7

8. In a power-hammer, the combination of a barrel, a power operated hollow cylinder having one end closed-and the other open deliver its full blow on the working 9. In a power-hammer, the combination of a barrel, a power operated hollow cylinder having one end closed andrthe other open, 1 reduced in diameter intermediate its ends to form an annular space between it and the inner walls of the barrel, and also having per or closed end of said cylinder above said so I rearward movement of the piston with the ,munication between the ports, and a movable'in'said cylinder, theports being so cylinder and the piston opens both ports on itsforward stroke to permit-the piston to deliver its full blow on the working tool.

10. In a power-hammer, the combination of a barrel, a power operated hollow cyl inder having one end closed and the other open and also having two ports at different points intermediate its length and in communication with the interior of the closed end of the cylinder, means affording comiston positioned that the pistoncloses but one port during part of its rearward stroke and causes a partial vacuum efl'ecting rearward movement of the iston with the cylinder and finally closes 0th ports near the end of such movement so that that-rapped air serves as a cushion for the piston, and the piston opens both ports on its forward stroke to permit the piston to deliver its full blow on the working tool.

v 11. In a power-hammer, the combination a of a barrel, a power operated hollow cylinder having one end closed and the other open and also having two ports at different points intermediate its length and in communication'with the interior of the closed end of the cylinder, mean affording communication between the ports, and a piston movablein said cylinder, the ports being so positioned that the piston closes one on its rearward stroke and causes a partial vacuum effecting rearward movement of the piston with the cylinder and the piston opens both ports on its forward stroke to permit the piston to deliver its full blow on the working tool, and said cylinder also having a port in communication with the open end of said cylinder and with the aforesaid ports through said means and opened by said piston during its rearward stroke.

g 12. In a power-hammer, the combination of a barrel, a power operated hollow cylinder having one end closed and the other open, means affording an annular space between'the cylinder and the inner walls of the barrel, said cylinder also having two ports at different points intermediate its length and in communication with the interior of the closed end of the cylinder and said annular space, the volume of the closed end of the cylinder above the plane through the upper port being substantially equal to the volume of said annular space, and a iston movable in said cylinder, the ports ing so positioned that the piston closes tween the cylinder and theinner walls of the barrel, said cylinder also having two ports at diflz'erent points intermediate its length and in. communication with the interior of the closed end of the cylinder and said annular space, the volume of the closed end of the cylinder above the plane through the upper port being substantially equal to the volume of said annular space, and a piston movable in said cylinder, the ports being so positioned that the piston closes only the lower one during the major portion of its rearward movement and causes-a partial vacuum effecting rearward movement of the piston with the cylinder, and the piston opens both ports .on its forward stroke,

said cylinder also having a port in communication with its open end and said annular space and uncovered by said piston near the end of its rearward stroke.

14. In a power-hammer, the combination of a barrel, a power operated hollow cylinder having one end closed and the other open, reduced in diameter intermediate its I ends to form an annular space between it and the inner walls of the barrel and also having two ports at different points intermediate its length and in communication with'the interior of the closed end, the volume of the closed end above the plane through the upper port being substantially equal to the volume of the annular space, and a piston movable in said cylinder, the ports bein so positioned that the piston closes the ower oneduring the major portion of its rearward movement and causes a' partial vacuum effecting rearward movement of the piston, closes the upper port near the end of such movement so the tra ped' air serves as a cushion and opens bot ports on its forward stroke.-

15. In a power-hammer, the combinatio of a barrel, a ower operated hollowcylinder slidably tting therein, said cylinder having ports at three different points intermediate its length and communicating with the interior of the cylinder, means affordingcommunication between the ports at the three points, and a piston movable in the cylinder and controlling the opening and closin of said ports.

16. n a. power-hammer, the combination of a barrel, a power operated hollow cylin-:

der slidably fitting therein, having one end open and also having ports at three diflib ferent points intermediate its length and Communicating with the interior of the cylinder, means affording communication between the ports, and a piston movable in said cylinder and adapted to deliver its blow on the working tool through the open end of the cylinder..

17. In a power-hammer, the combination of a barrel, a power operated hollow cylinder therein having its lower end open, reduced in diameter intermediate its ends to form an annular space between it and the inner walls of the barrel and having ports at three different points intermediate its length and communicating with its interior and said annular space, and a pistonmovablein said cylinder and adapted to open and close said ports and to deliver its blow on the working tool through the open'end of the cylinder.

JOHN WILLIAM CUNNINGHAM. 

